The present invention relates to a light scanning type confocal optical device, which scans light emitted from a light source over the surface of an object, and detects light reflected from the surface or fluorescence, and also relates to a light scanning device applied to the optical device.
In recent years, the light scanning type confocal optical microscope has been known as means for minutely observing living tissue or the surface or the inside of cells. The confocal optical microscope has a resolving power exceeding that of an ordinary optical system and, in addition, can obtain a three-dimensional image. However, an ordinary confocal optical microscope has a large optical system, and can not practicably be inserted into the living body. Thus, in general, living tissue is removed from the body in order for the tissue to be observed with the ordinary confocal optical microscope.
In order to overcome this disadvantage, a smaller optical system of a light scanning type micro-confocal microscope is disclosed in the literature "Micromachined scanning confocal optical microscope" (OPTIC LETTERS, Vol. 21, No 10, May, 1996) or U.S. Pat. No. 5,742,419.
The literature suggests the possibility with which a three-dimensional image could be obtained in real time. To be more specific, the above light scanning type micro-confocal microscope, as shown in FIG. 8, comprises a light source 1, a light transmitting section 2, a light detecting section 3, a light scanning section 4, and a processing section 5. The light transmitting section 2 has a single mode fiber. The light scanning section 4 is inserted into the living body through an endoscope. By virtue of this, a three-dimensional image of the inside of the living body could be obtained in real time.
FIG. 9 shows the structure of the light scanning section 4. In the light scanning section 4, a laser light is emitted from the light source 1, and transmitted through the single mode fiber 10. Then, it is reflected by a reflection surface 11, and deflected in an X direction by an electrostatic mirror 12 for scanning light in the X direction. Thereafter, it is totally reflected by a reflection portion 14, deflected in a Y direction by an electrostatic mirror 13 for scanning light in the Y direction, and then converged onto an object surface 16 by a diffraction lens 15.
An end face of the single mode fiber 10 has a conjugate relationship with the object surface 16. Accordingly, the light reflected from the object surface 16 turns back on the above optical path, and converges on the end face of the single mode fiber 10. To be more specific, the light reflected from the object surface 16 is incident on the diffraction lens 15, and thereafter reflected successively by the electrostatic mirror 13, the reflection portion 14, the electrostatic mirror 12, and the reflection surface 11 in that order. Then, it is converged on the end face of the single mode fiber 10 by a converging function of the diffraction lens 15. The converged light is transmitted through the single mode fiber 10 of the light transmitting section 2, and detected by the light detecting section 3.
The above optical system composes a confocal optical system, since the end face of the core of the single mode fiber 10 functions as a pinhole. Thus, scattered light from that portion of the object surface 16 which excludes a convergence point is sufficiently weak in intensity at the end face of the fiber 10, and hardly detected by the light detecting section 3.
Therefore, the above optical system has high resolution in a horizontal direction (XY direction) of the object surface 16 and a depth direction (Z direction) of the object surface 16, as compared with the ordinary optical system. In other words, it has higher longitudinal and transverse resolving powers than the ordinary optical system.
The above light scanning type micro-confocal optical microscope has a lower resolving power than the ordinary confocal optical microscope; however, its resolving power is sufficient for diagnosis involving observation of an internal organ or the like. In addition, the micro-confocal optical microscope has a considerably compact structure.
In insertion of such a micro-confocal optical microscope into the living body through the endoscope to observe the inside of the body, its view direction obliquely crosses its insertion direction. Accordingly, it is difficult to accurately move the object surface 16 in the Z direction only. In other words, the above micro-confocal microscope has bad observational operability.
Furthermore, the conventional micro-confocal microscope uses two reflection surfaces 11 and 14 and two one-dimensional scanning mirrors 12 and 13, in order to achieve two-dimensional scanning. However, use of such a large number of reflection surfaces causes attenuation of light due to reflection performed between the large number of surfaces, thus lowering the detection sensitivity.